basics of geometry 2013.ppt

7/27/2019 basics of geometry 2013.ppt

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Basics of Geometry


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Basics of Geometry


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Basics of Geometry


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Basics of Geometry

Basics of Geometry

POINTS!

LINES!

PLANES!


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Basics of Geometry

The terms points, lines, and planes are the foundations ofgeometry, but

point, line, and plane are all what we call undefined terms.

Undefined Terms?


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Basics of Geometry

Has no dimension Denotes or represents a position or location

Usually represented by a small dot

Point

A

The above is called point A ( A). Note the

point is represented with a capital letter.


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Basics of Geometry

Has one dimension (length)

Extends indefinitely in both directions without end

Represented with straight line with two arrowheads to

indicate that the line extends without end in two directions.

Line

l

B

A

This is Line l, (using the lower case script

letter) or symbolically we call it .AB

NOTICE: The arrowheads are in

both directions on the symbol

AB


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Basics of Geometry

Plane Extend in two dimensions.

Represented by a slanted 4 sided figure, but you

must envision it extends without end, even

though the representation has edges.

A

B CM This is Plane Mor plane ABC

(be sure to only use three of the

points when naming a plane)


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Basics of Geometry

Undefined Concepts

Collinear points are points that lie on the

same line.

l

C

AB Points A, B and C are collinear.


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Basics of Geometry

Undefined Concepts

Coplanar points are points that lie on the

same plane.

A

BC Points A, B and C are coplanar.


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Basics of Geometry

Line Segment

Here is line AB, or recall

symbolicallyAB

A B

The line segment does not

extend or without end. It has

endpoints, in this case A and

B. The segment contains all

the points on the line

between A and B

A B

Notice the difference in

the symbol!

This is segment AB

It is a part of a line or subset of a line.


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Basics of Geometry

Symbolized by

Ray

AB

The initial point isalways the first

letter in naming a

ray. Notice the

difference in

symbols from both

a line and segment.

A B

A is called the initial

point

Ray AB extends in

one direction

without end.

Lets look at a ray:


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Basics of Geometry

Not all symbols are created equal!

Symbol alert!

BAAB is the same as

AB BAis the same as

BUT

A B

A B


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Basics of Geometry

AB is not the same as BA

Symbol alert!!

A B AB

A B BA

Initial point 1stThe ray is different!

Notice that the initial point is listed first in the symbol. Also note

that the symbolic ray always has the arrowhead on the right

regardless of the direction of the ray.


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Basics of Geometry

Name the geometric concept represented by each.

Quick Quiz!!!

1. tip of a pen

2. top of a table

3. edge of a computer table

4. head of pin

5. wire


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Basics of Geometry

Name the geometric concept represented by each.

Quick Quiz!!!

6. clothesline

7. train track

8. chalkboard

9. shoe laces

10. beam of light


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Basics of Geometry

Quick Quiz !!!!1. Name 3 points that are collinear.

Points D, F and B lie on the same line, therefore they are collinear.

2. Name 4 points that are coplanar.

If you answered D, F, B, and G are coplanar, then you are correct. It is

harder to see because the plane is not drawn, but points D, F, B and M

are also coplanar.

3. Name 3 points that are not collinear.

There are many correct answers, D, F, M are not

collinear.

M

G

DF

B

basics of geometry 2013.ppt

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